In contrast with liquid crystal displays (LCD), organic electroluminescent displays are self-luminous and require no backlight. Thus, the weight can be reduced and the size can be minimized. Moreover, organic electroluminescent displays feature low driving voltage, high illumination efficiency, and wide view angle, thus obtaining attracted wide attention.
An organic electroluminescent display comprises a plurality of organic light-emitting display (OLED) devices for displaying images. Each OLED comprises an anode, an organic light-emitting layer and a cathode. The anode and the cathode provide holes and electrons to the organic light-emitting layer, where the holes and the electrons are recombined to form excitons. When the excitons settle down to a bottom steady state, they generate light with predetermined wavelengths. According to material characteristics of the organic light-emitting layer, light with wavelengths corresponding to, for example, red, green and blue, is generated.
In the organic electroluminescent display, each organic light-emitting layer realizing red (R), green (G) and blue (B) should be laid out for each pixel, so as to achieve full color display. The conventional manufacturing process of an OLED device comprises vacuum deposition, jet-printing, nozzle-printing, laser ablation, laser induced thermal imaging or the like. Among these methods, devices with best characteristics are produced by a vacuum deposition process. However, the vacuum deposition requires a fine metal mask (FMM) to generate a layout required by the high-resolution display. FMM has many problems such as high cost for mass production, and difficulties for stretching and maintenance. Moreover, it is necessary to accurately align FMM with the substrate before deposition starts. For a large-sized substrate, the alignment is difficult, especially when high resolution is required. In addition, the alignment process further requires complicated accessories to be added into the evaporation chamber for dealing with the alignment process.